National Instruments Welding System 321645c-01 Manual Do Utilizador
Chapter 2
Function Reference — GPCTR_Set_Application
NI-DAQ FRM for PC Compatibles
2-238
©
National Instruments Corporation
6602 and 455X devices with counter width 32 bits, you can generate pulses with a delay and
length between 100 ns and 214 s long.
length between 100 ns and 214 s long.
Figure 2-25. Buffered Period Measurement
Typically, you will find modifying the following parameters through the
GPCTR_Change_Parameter
function useful when the counter application is
ND_BUFFERED_PERIOD_MSR
. You can change the following:
•
ND_SOURCE
to
ND_INTERNAL_100_KHZ
. With this timebase, you can measure intervals
between 20 µs and 160 s long. The resolution will be lower than if you are using
ND_INTERNAL_20_MHZ
timebase.
•
ND_SOURCE_POLARITY
to
ND_HIGH_TO_LOW
•
ND_GATE
to any legal value listed in the
GPCTR_Change_Parameter
function
description
•
ND_GATE_POLARITY
to
ND_NEGATIVE
. Measurements will be performed between
successive high-to-low transitions of the signal present at the gate.
To provide your timebase, you can connect your timebase source to one of the PFI pins on the
I/O connector and change
I/O connector and change
ND_SOURCE
and
ND_SOURCE_POLARITY
to the appropriate values.
You also can configure the other general-purpose counter for
ND_PULSE_TRAIN_GNR
, and set
ND_SOURCE
of this counter to
ND_OTHER_GPCTR_TC
to measure intervals longer than 160 s.
Note
The counter will start counting as soon as you arm it. Be aware of this when you
interpret the first count in your buffer.
interpret the first count in your buffer.
Caution
If gate edges arrive and no source edges are present between those gate edges, then
the previously saved value is saved again as shown in Figure 2-25. Please make
sure that this condition does not occur during your measurement.
the previously saved value is saved again as shown in Figure 2-25. Please make
sure that this condition does not occur during your measurement.
Source
Gate
Buffer
2
1
4
3
6
5
1
7
3
2
5
4
1
6
3
2
4
Measured
Period
Measured
Period
Measured
Period
7
7
6
7
6
4
!